MONDAY, April 29 (HealthDay News) -- Men who are obese in their early 20s have a significantly increased risk of dying or of having serious health problems such as diabetes and heart disease by the time they reach age 55, a new long-term study indicates.

Researchers tracked the health of 6,500 Danish men from age 22 until age 55. At the start of the study, 83 percent of the young men had normal weight, 5 percent were underweight, 10 percent were overweight and 1.5 percent were obese.

Compared to those with normal weight, obese young men were eight times more likely to develop diabetes, four times more likely to have a potentially fatal blood clot, and more than twice as likely to develop high blood pressure, have had a heart attack or to have died, according to the study published April 29 in the online journal BMJ Open.

Every unit increase in body mass index (a measure of body fat based on height and weight) was associated with a 5 percent increased risk of heart attack, a 10 percent increased risk of high blood pressure and blood clots, and a 20 percent increased risk of diabetes.

Overall, obese young men had a nearly 50 percent risk of developing any of these serious health problems by middle age, compared with a 20 percent risk for young men with normal weight, according to a journal news release.

The findings suggest that rising rates of obesity may counteract the decrease in deaths from heart disease, and place a huge burden on health care systems worldwide, concluded study author Henrik Toft Sorensen, a professor at Aarhus University Hospital in Denmark, and colleagues.

The study found an association between obesity in young men and a greater risk of serious health problems or death by age 55. However, it did not prove a cause-and-effect relationship.